- Redbush tea (South Africa)
- Rooibosch (Netherlands)
For Patients & Caregivers
How It Works
Rooibos tea is rich in antioxidants which may protect against cancer and other diseases. However, these effects have not been shown in humans.
Rooibos tea contains compounds that may prevent tumor growth and aging processes, but the specific mechanisms are not known. Further studies are needed. Some compounds isolated from rooibos leaves showed estrogenic activity. Patients with hormone-sensitive cancers should use caution before taking rooibos.
For Healthcare Professionals
Prepared from the dried leaves of the rooibos plant native to South Africa, rooibos tea has grown popular in western countries because it is rich in antioxidants, especially the polyphenols aspalathin and nothofagin (1), and low in caffeine. It does not contain any catechins, the major flavonoids present in green and black teas (2).
In vitro and animal studies have shown that rooibos can modulate immune function (3) (4), exhibit anti-inflammatory effects (5), may prevent oxidative stress and play a role in alleviating symptoms associated with type-2 diabetes (7).
Animal studies also suggest that it may prevent chromosomal aberrations (8) and tumor mutagenesis (9) (10).
Topically applied rooibos elicits a protective effect against microsomal lipid peroxidation and may help reduce chemical-induced tumor formation (1) (11). Rooibos also appears to protect against damage caused by radiation (12). However, these effects have not been confirmed in humans.
Rooibos was shown to inhibit angiotensin-converting enzyme in healthy volunteers (2), which may benefit cardiovascular health. Further research is needed.
Because compounds isolated from rooibos leaves demonstrated estrogenic activity (22), patients with hormone-sensitive cancers should use caution before taking rooibos.
Mechanism of Action
Rooibos was shown to enhance the activity of glutathione-S transferase and UDP-glucuronosyl transferase in rat liver (11) (16), allowing cells to protect against oxidative stress, and to reduce the effects of hepatocarcinogens. A study of oxidative stress in rats found that serum superoxide dismutase and urine 8-hydroxy-2’-deoxyguanosine (8-OHdG) concentrations (as markers for DNA damage) were significantly reduced following administration of rooibos (17). Some studies have shown that the non-oxidized teas have greater antimutagenic effects compared to the oxidized forms. This is probably due to reduction in total polyphenol content with oxidization (11) (18) (19). The anti-inflammatory effects of rooibos are thought to be due to its inhibition of COX-2 enzyme (5).
In other studies, rooibos significantly decreased glucocorticoid levels in rats and steroid metabolite ratios linked to metabolic disorders-cortisol:cortisone in humans and CORT:testosterone in rats (23). Hot water-soluble solids from fermented rooibos inhibited adipogenesis and influenced adipocyte metabolism, suggesting a role in preventing obesity (24).
- Rooibos tea may cause hepatotoxicity (21).
A study done in male rats indicates that prolonged exposure rooibos might result in subtle structural changes in the reproductive system and may induce acrosome reaction, which can impair fertility. Intake of large amounts of rooibos may also harm liver and kidney function (25).